Meiosis

• Meiosis (general)

  • form of eukaryotic cell division with the production of gametes in sexually reproducing organisms
  • type of cellular division involving 1 cycle of DNA replication and 2 rounds of cell division
  • results in the production of 4 non-identical haploid daughter from each original diploid cell
• Meiosis I (prophase I)

  1. duplicated homologous chromosomes pair up and exchange segments
  2. crossing over occurs leading to genetic recombination
• Meiosis I (metaphase I)

  1. chromosomes line up in homologous pairs and align at the metaphase plate (equator)
  2. spindle fibres attach to the centromeres of each homologous chromosome
• Meiosis I (anaphase I)

  1. each pair of homologous chromosomes separate and move to opposite poles of the cell
• Meiosis I (telophase/cytokinesis I)

  2 haploid cells form; each chromosome still consists of 2 sister chromatids
• Crossing Over

  • the swapping of alleles that occurs in the germ line during prophase 1
  • allows the exchange of alleles between the maternal and paternal homologous chromosomes
• Independent Assortment

  • occurs in eukaryotic cells due to random orientation of maternal and paternal chromosomes during metaphase
  • when gametes are formed, the assortment of one pair of chromosomes between the daughter cells is independent to another pair
  • homologous pairs line up with the 2 paternal chromosomes either on the same or opposite side of the metaphase plate
  • results in different genetic combinations